Figure 4-4 Functional Overview Block Diagram Of Internal Cascade Controller; Output Override - Honeywell UDC3500 Product Manual

Loop 1 is the secondary (internal or slave) loop.
•
Loop 1 Remote Setpoint is fixed as the Loop 2 output.
•
LOOP 2 – PRIMARY LOOP
S ETPOINT
S OURCE
S e e Loo p
Blo c k Diag ram
INTERNAL CAS CADE RULES
• Loop #2 is the prima ry (e xte rna l) loop.
• Loop #1 is the s e conda ry (inte rna l or s la ve ) loop.
• Loop #1 Re mote S e tpoint is fixe d a s loop #2 output.

Figure 4-4 Functional Overview Block Diagram of Internal Cascade Controller

Output Override

This instrument allows override of the Loop 1 output with the Loop 2 output based upon
which is larger or smaller. This can be accomplished by configuration (See Section 3.8)
or by Digital Input actuation (see Section 3.19).
The following rules apply for high/low override:
Only one physical output is required when override is enabled. It is the output
•
from Loop 1 because Loop 2's internal output is routed through the selector.
Loop 2 output can also be available at all times if desired.
•
In Manual mode, the Output may be overridden.
•
Does not apply for Three Position Step Control.
•
OTI on bottom display shows value of the internal Loop 1 output before any
•
override.
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PV S OURCE
S e e Blo c k
Diag ram
PID
CONTROL
ALGORITHM
INTERNAL
OUTPUT
S IGNAL
UDC3500 Universal Digital Controller Product Manual
Monitoring and Operating the Controller
LOOP 1 – S ECONDARY LOOP
S ETPOINT
S OURCE
S P
2S P
Lo c al S e tpoint
3S P
4S P
Re mo te S e tpo int
PV S OURCE
S e e Blo c k
Diag ram
PID
CONTROL
ALGORITHM
OUTPUT
To Final
Co ntro l
Eleme nt
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